Method of cutting slots in metal



C. J. COBERLY METHOD OF .CUTTING SLOTS IN METAL April 17, 1928,

Filed Dec. 2, 1925 E //Z w H K M w a 6 a a Patented Apr. 17, 1928.

UNITED STATES PATENT OFFICE.

CLARENCE J. COBERLY, 013 LOS ANGELES, CALIFORNIA, ASSIiGNOR TO. KOBE, INC., 0] LOS ANGELES, CALIFORNIA, A CORPORATION OI! CALIFORNIA.

METHOD OF CUTTING SLOTS IN METAL.

Application filed December 2, 1925. Serial No. 72,690.

My invention relates to the art of cutting slots in metal by use of a cutting torch, and particularly to a method and apparatus whereby slots may be expeditiously and accurately cut in metal. w

In an application entitled Pipe slotting macliiine, liled October 1, 1928, Serial No. (365,917, I have described a. machine and a method whereby slots are cut in a metal by use of a cutting torch. Briefly, the method consists in drilling a starting hole in the metal (which in the mentioned case was a steel pipe to be made intoa well strainer) for providing a start for a slot, and cutting a slot in the metal by use of a cutting torch, this slot being started at said starting hole.

I have discovered that by preheating the metal the slot may be quickly and accurately out, since the cutting torch operates more effectively on metal at a high temperature;

It is, therefore, an object or" this invention to provide a method of cutting a slot in metal in which the metal. is preliminarily heated and the slot is out while the metal hot.

In my method I prefer to heat-the metal alter the starting hole has been drilled so that the drill may operate on cold metal, since drilling in hot metal. would take the temperout of the drill.

It is, therefore, another object of my in vention to provide a method for forming a slot in a metal whichconsists in driilinga starting hole, then preliminarily heating the n'letal and finally cutting the slot.

It is another object of this invention to provide an apparatus for forming. slots in a metal, having a means for heating the metal before the cutting of the slot.

It is a further object oi? this invention to provide an apparatus of the character mentioned having a heater in the torm ot aninduction heater.

I have further found that in cutting slots in steel pipe, the hardness of the surface of the slot depends on the rate of cooling after the cutting flame has passed and on the analysis of the steel, particularly the carbon content. In slotting the low carbon steels used in Welded pipe, the cooling due to the flow of heat to the metal back of the heated creasing the hardness and strength. In some cases it is desirable to increase the rate of cooling by quenching with an air blast or other means, as disclosed in my application Serial No. 665,917. In slotting steel of higher carbon content (.40% to .60% carbon) as aresometimes-used in making seamless steel pipe, the above means of quenching causes too great an increasein hardness and a reduction of ductility, in some cases even causing microscopic cracks on the surface of the slot which are detrimental in that theyform favorable places for a fracture to start. In other words, the hardness is increased to a point where the metal is brittle, which is undesirable in slotted pipe subject to severe strain and abrasion.

l have found that this hardness can be controlled and that the metal around the slot can be made stronger and harder than the original metal without loss of ductility by proper control of the initial temperature 01' the steel. This works in two ways to acis equivalent to drawing the temper after quenching. Second, and more important, the rate of conduction of heat from the complishthe desired result. First, the metal I being init ally at an elevated temperature metal in the zone raised to a veryhigh temperature by thecutting action is greatly reduced by increasing theinitial temperature of the steel. Hence, raising the initial temperature of the steel 500 F. is much more effective than raising it to this'temperature a second operation after cutting.

In comparing this process with the usual methods of heat-treating steel, it should be trolled by means of the initial temperature of the steel. i

It is accordingly an object of thisinvention to. provide a method of heat-treating steel as previously explained and partied larly at the time slots are formed therein.

By means of this process it is possible to accurately control the conditions so as to ob tain the maximum hardness and toughness for each grade of steel with the result that the resistance to sand abrasion and the strength of the casing are greatly increased.

Other objects and advantages of my invention will be made evident hereinafter.

Referring to the drawings in which 1 illustrate an apparatus whereby my invention may be carried out,

Fig. 1 is a cross section through an ap paratus of my invention.

Fig. 2 is a section taken on the line 2 2 of Fig. 1.

The "form of apparatus shown in the drawings is adapted to cut slots in a pipe indicated at 1.1. A trame 12 surrounds the pipe 11. This frame 12 consists of annular plates 13 and. 14 which are secured together by a cylindrical member 17 having flanges 18 which are secured to adjacent faces of the plates 13 and 14: by suitable cap screws 19. I

Secured to the outer "face of the plate 14; in any suitable manner is a plurality of drill devices 20 having drills 21. The devices 20 have pulleys 22 which are operated by belts (not shown) for rotating the drills 21. The drill devices 20 are constructed so that the drills 21 may be automatically fed into the Wall of the pipe 11 in order to term starting holes 2 1 and also to be automatically with drawn therefrom. The drill devices 20 may be of the sameconstruction as shown in my application mentioned in the preambleot this specification,

Extending inwardly from the cylindrical member 17 is an annular flange 27 to which an annular flange 28 of an induction heater 30 is secured by screws 81. This induction heater .30 has coils 83, 34, and 35, which have wires 37 of a threepl1ase circuit connected thereto. Also connected to the coils 33, 34 and 35 are ground wires 38 which extend to a ground, as diagrammatically indicated in Fig. 1. The coils 33, 3 1 and are annular and completelysurround the pipe, as shown in Fig. 2. When the coils are energized, magnetic lines of force are set up, which lines of force set up induced electric currents in the wall of the pipe 11., heating it to the desired temperature.

Secured to the outer face of the annular plate 13 of the frame 12 is a plurality of cutting torches 4:0. The cutting torches ll) have tips ll which are positioned adjacent to the wall of the pipe 11. The cutting torches 10 are supplied with oxygen and acetylene gasthrough conduits 42 and 13. The tips 41 of the torches are so positioned as to align with the starting openings 24: produced by the drills 21 and are adapted to form slots in the pipe 11, as indicated at 45. p

A complete operation of my invention is substantially as follows:

well strainers 01 a uniform size.

The induction heater 30 is set into opera tion by supplying electricity therethrough to the wires 37 which set up magnetic lines of force which cut the wall of the pipe 11 and induce electric currents therein which in raise it to the proper temperature, which is preferably such as will. permit the torches to readily heat the pipe to an oxidizing temperature. The drill devices 20 set into operation and the drills 21 are rotated and fed inwardly into the wall of the pipe 11 in a manner to produce the starting holes 2-1-. The drills 521. are withdrawn. The tips 11 ot the cutting torches 4-0 are at this time in alignment with a series oi? starting holes 2ft. The torches 40 are then lighted by automatic means. The frame 12 is supported by means (not shown) whereby it may be moved along the pipe 11. in a right hand direction. the frame 12 moves, the cutting 3 jets produced by the torches 40 are moved. therewith and slots 45 are formed by the action of the jets oi the torches. The frame 12 is moved through a suilicient distance to pro ide the desired length o'l. slot. The frame is then stopped and the torches 4.0 are shut down. The drill devices 20 are again set into operation and the scquei'ice of oper ations just described repeated.

As previously mentioned, by providing the heater 30 for preheating the pipe 11 it is possible to quickly cut the slots :.5 and to cut them very accurately, so that they will have very smooth walls and will be of a uniform size which is highly desirable. My in- "vention is very well suited for use in making well strainers for the oil well industry and it very desirable to have the slots in t is well known in the welding industry that in order to cut metal, it is necessary to preheat it to a temperature which approaches the fusing point of the meta-hso that the oxygen when suppliedto the torch will be able to burn the metal away. By using the heater 30 it is possible to raise the temperature of the pipe 11 to a desirable temperature so that the metal may be readily and, efi'cctively burned away.

Another important adi 'antage of the invention is the hardening of the metal, which is advantageous especially when the pipe is used as a well strainer because oil generally carries small particles of abrasive which tend to wear away the walls of the slots. The induction heater very quickly raises the temperature to a determined degree which is highly desirable, and the metal will cool evenly and at a uniform rate. The heater may be regulated to heat the pipe to any desirable temperature and the hardening oi? the pipe may be thus controlled. Alter the walls of these slots are hardened, they will resist the attritional action of the abrasive particles. The heater 30 is placed be- 139 tween the drill devices 20 and the torches 40 so that the pipe 11 will be heated after the starting holes are produced so that the drill 21 will operateon cold metal and so that the temper will not be taken therefrom.

I claim as my invention:

l. A method of forming a slot in a piece of metal and determining the rate of quench ot the walls of said slot, said method comprising: uniformly heating an extensive area of said metal; directing a cutting jet through said metal in an interior portion of said extensive heated area to form a slot in said metal, the difference in temperature between the walls of said slot and said extensive area of metal being much less than otherwise, due

to said uniform heating of said extensive area; and permitting said metal to cool gradually, the temperature of said extensive area determining the rate of quench of the walls of said slot.

2. A method of forming a slot in a piece of metal and determining the rate of quench oi the Walls of said slot, said method comprising: heating an extensive area of said metal; directing a cutting jet through said metal in an interior portion of said extensive heated area to form a slot in said metal, the di'li'erence in temperature between the walls of said slot and said extensive area of metal. being much less than otherwise, due to said heating of said extensive area; and permitting said metal to cool gradually, the temperature of said extensive area determining the rate of quench of the walls of said slot.

A method of slotting pipe, said method comprising: forming starting holes in said pipe; substantially uniformly heating an extensive zone of said pipe; directing cutting jets through certain holes in said zone; moving said pipe relative to said jets whereby slots are formed in an interior portion of said zone; and allowing said pipe to cool gradually, the heat applied to said zone preventing too rapid cooling of the walls of said slots. I

4:. A method of slotting high carbon steel pipe, said method comprising: forming starting holes in said pipe; substantially uniformly heating an extensive zoneof said pipe to a temperature above 400 F.; directing cutting jets through certain holes in said zone; moving said pipe relative to said jets whereby slots are formed in an interior portion of said zone; and allowing said pipe to cool gradually, the heat applied to said zone preventing toov rapid cooling of the walls of said slots.

5. A method ofslotting pipe, said method comprising: forming startin holes in said pipe; substantially uniformly heating an annular zone of said pipe; directing cutting jets through certain holes in said zone; moving said pipe relative to said jets whereby slots are formed in aninterior portion of said zone; and allowin said pipe to cool gradually, the heat applied to said zone preventing too rapid cooling of the walls of said slots.

6. A method of slotting pipe, said method comprising: causing heat rays to converge toward a given space; forming a hole in a zone of a pipe; extending said zone into said space, for a suflieient length of time to heat said zone uniformly to a given temperature; forming a hole in a portion of said pipe which has not yet been extended into said heating space, while said zone is being heated; moving said pipe to a new holeforming and heating position; and directing a cutting jet through the hole in said zone a While said pipe is being moved in order to form a slot in said zone.

7. A method of cutting a slot in metal with a wall of predetermined hardness said method comprising: preheating-an extensive area of said metal to a desired temperature;

, directing a cutting jet through said metal in said extensive area to form a slot in said area; and permittingsaid metal to cool so as to quench a wall of said slot, the length of time consumed by said quenching being determined by the difference between the temperature given said wall in the cutting of said slot and the temperature to which said extensive area was heated.

8. A method of formingv a slot in metal and controlling the hardness of a wall of said slot said method comprising: uniformly heating an extensive area of said metal;

directing a cutting jet through said metal in said extensive heated area to form a slot in said metal; and quenching a wall of said slot, the difference between the temperature given said wall in the cutting of said slot and the temperature to which said extensive area was uniformly heated affecting the rate of quench of said wall.

In testimony whereof, I have hereunto set my hand at Los Angeles, California, this 25 day of November, 1925.

CLARENCE J. COBERLY. 

